The present invention pertains generally to the field of medicine, and more particularly to positioning an interventional device in a body using a medical imaging system.
Computed tomography (CT)-guided biopsies have been performed since the early days of CT scanning when it became apparent that the cross sectional imaging modality offered unprecedented abilities to visualize the needle in cross section to verify positioning within a lesion. Over the last 15 years, the methodology for the CT-guided biopsy has remained largely one of trial and error. Essentially, a scan of the appropriate body part is made and a mental calculation of the trajectory is made following a depth calculation on the computer console. The depth is then transferred to the interventional device which has been marked. The interventional device is then inserted, removed, and reinserted repeatedly with repeat scanning at the appropriate interventional device position to confirm proper placement or improper placement. Obviously, this technique of trial and error introduces undesirable delays, risks, costs and, in some cases, exposure to unwanted radiation.
In addition to the matter of CT-guided biopsies, there has been much recent work in the field of MR-guided surgery, including biopsies and other minimally-invasive procedures. At present, methods of trajectory localization under MR are based largely on frameless stereotactic concepts. While this is a feasible methodology for many situations, there remains an issue of cost. To date, there has not been a method proposed that is simple, accurate, and inexpensive for use in the MR setting.
Therefore, there remains a need for a method for locating a interventional device in a body part which is faster and more convenient.
According to one example embodiment, the present invention provides a method of positioning an interventional device in a body using a guide pivoting about a pivot point, comprising locating the spatial coordinates (or the image display of a point corresponding to said coordinates, even if said coordinates are not explicitly stated because a computer is capable of interpreting the mathematical relationship of the display to the true coordinates) of a target and the pivot point, determining a third point outside of the body lying along or proximate a line extending through the target and pivot point, and aligning the axis of the guide with the third point using an imaging system.
According to another example embodiment, the invention provides a medical imaging system including a processing unit and computer software operative on the processing unit to permit an operator of the system to locate the spatial coordinates of a target point and a pivot point of a guide, and determine a third point outside of the body lying along or proximate a line extending through the target and pivot point. This medical imaging system may further include computer software operative on the processing unit to assist an operator in obtaining an image by which the axis of the guide can be aligned with the third point using an imaging system.
According to another embodiment, the invention provides a method of using the MR signal from one or more radiofrequency microcoils placed on the trajectory alignment stem at the pivot point and at the at least third point to determine the spatial locations of these two coils, and hence the position of the alignment stem, including its orientation. Moreover, with this information determined and therefore known to the MR scanner computer, the trajectory alignment stem could be realigned to match the desired trajectory, either manually, by remote or robotic control, or by control of the MR scanner computer itself, by means of an interface with a servo mechanism either directly or indirectly attached or related to the trajectory alignment stem.
According to another embodiment, the invention provides an article of manufacture comprising a computer program encoded in a carrier, wherein the program is operative on a processing unit of a medical imaging system to permit an operator of the system to locate the spatial coordinates of a target point and a pivot point of a guide, and determine a third point outside of the body lying along or proximate a line extending through the target and pivot point.
According to yet another embodiment, the invention may provide that the axis of the guide is aligned automatically under software control.